Publications

Based on the concept of band bending at metal/semiconductor interfaces as an energy filter for electrons, we present a theory for the enhancement of the thermoelectric properties of semiconductor materials with metallic nanoinclusions. We show that the Seebeck coefficient can be significantly increased due to a strongly energy-dependent electronic scattering time. By including phonon scattering, we find that the enhancement of ZT due to electron scattering is important for high doping, while at low doping it is primarily due to a decrease in the phonon thermal conductivity. © 2008 The American Physical Society.

Abstract not provided.

We present an ab initio method for electronic structure calculations of materials at finite temperature (FT) based on the all-electron quasiparticle self-consistent GW (QPSCGW) approximation and Keldysh time-loop Green's function approach. We apply the method to Si, Ge, GaAs, InSb, and diamond and show that the band gaps of these materials universally decrease with increasing temperature in contrast with results of the local density approximation (LDA) of density functional theory where the band gaps universally increase. At temperatures of a few eV the difference between quasiparticle energies obtained in FT QPSCGW and FT LDA approaches is significantly reduced. This result suggests that existing simulations of very high-temperature materials based on the FT LDA are more justified than it might appear from the well-known LDA band gap errors at zero temperature. © 2006 The American Physical Society.

Abstract not provided.

Abstract not provided.

We present nanometer-scale resolution, ballistic electron emission microscopy (BEEM) studies of Au/octanedithiol/n-GaAs (001) diodes. The presence of the molecule dramatically increases the BEEM threshold voltage and displays an unusual transport signature as compared to reference Au/GaAs diodes. Furthermore, BEEM images indicate laterally inhomogeneous interfacial structure. We present calculations that address the role of the molecular layer at the interface. Our results indicate that spatially resolved measurements add new insight to studies using conventional spatial-averaging techniques.

Abstract not provided.